Fertility substantially damaged by delaying fatherhood

Delaying fatherhood can substantially harm a man's chance of having a family, new research suggests.

A study of more than 20,000 couples seeking fertility help shows that middle-aged men are almost a third less likely to conceive with their partner than males under 35.

The findings, to be presented today at the European Society of Human Reproduction and Embryology conference in Barcelona, could signal that men need to consider their age when planning a family as much as women do.

Doctors have long warned that too many young women are putting off starting a family until their late thirties or early forties, by which time their fertility levels have started to fall.

But the example of older celebrity fathers, including Sir Paul McCartney and Rod Stewart, have encouraged many men to believe that they can postpone having children for much longer than women.

However, the research at the Eylau Centre for Assisted Reproduction in Paris found that the older a prospective father, the less chance that their partner would become pregnant. The study involved a form of fertility treatment, where the sperm is "washed" before being inseminated into the woman. This helps the sperm to survive for longer.

For men between 30 and 35 the successful pregnancy rate was 13.6 per cent. But that fell to 9.3 per cent if the man was older than 45, a decrease of almost a third

The findings also showed that men over 35 were 75 per cent more likely to have their partner suffer a miscarriage. Although lower than the miscarriage rate for older mothers, which was more than twice that of younger mothers, the researchers still described it as significant.

They believe there could be a number of reasons behind the findings, including that the DNA of sperm decays over time.

Professor Yves Menezo, who was involved in the study, said: "We found that by around the age of 40 men were starting to face serious problems. Much more work needs to be done to understand why."

Fertility specialists warned that the results could be an early warning for men who want to be fathers in the future.

Dr Gillian Lockwood, the medical director at the Midland Fertility Services clinic in Wolverhampton, said: "We have known for some time that there are specific genetic condition, for example autism, that are linked to older fathers. However, the fact that older sperm is just not as good as younger sperm is very interesting indeed.

"Often you find that the 34-year-old woman is ready to settle down and have children but the 34-year-old man is not because he believes he has another 20 years left.

"Maybe men should realise that is not necessarily true."

She added that the results could have a profound effect on the use of volunteer sperm donors, numbers of which have fallen dramatically since a decision to overturn their guarantee of anonymity.

"We have been told to target older men who have finished their families, and would be less fazed by children contacting them in the future," said Dr Lockwood.

"But this study raises serious questions about the viability of that sperm."